A test for comparing the means of two samples, or the mean of one sample (or even parameter estimates) with a specified value; also known as the "Student t-test" after the pseudonym of its inventor.

learn more… | top users | synonyms

0
votes
0answers
9 views

How to interpret the student t statistic in a sas proc univariate output [duplicate]

I ran a proc univariate on a SAS data set and one of the output results was: ...
2
votes
1answer
32 views

Why bother looking at an omnibus ANOVA when I have a priori hypotheses about group differences?

I am examining three independent groups that were measured on a continuous outcome variable. I have a priori belief that the result should be Group 1 < Group 2 < Group 3. I've been told to do an ...
0
votes
0answers
18 views

paired or unpaired t-test

We are polling respondents every month and asking a couple of questions about the number of times they eat certain foods. We have significant loss to follow up every month but generally retain 20% - ...
0
votes
1answer
20 views

Likert scale question

I have a 13 item likert scale with 5 responses on each question. I am using the same questionnaire before and after intervention on the same group of people. What is the best way of analysing this ...
2
votes
1answer
43 views

How do I report a 95% CI in a one sample t test?

How do I report a negative 95% CI in a one sample t test? What does this mean?
0
votes
0answers
18 views

t.test applied in pairs to more than two samples in R

I have 44 samples where I only have its sample size, average and 1 standard deviation. I asked about the possibility of doing a t.test and some of you returned the answer: ...
2
votes
2answers
43 views

How to interpret the means of different sample sizes

I have three sets of data I am working with. The N of each are all vastly different and the means are also very different. I obviously don't want to interpret it so black and white because I know the ...
0
votes
0answers
16 views

Need help determining which statistical test to use

I am an MD attempting to do my own statistics for a project I have been working on. I have 3 groups (which are comprised of combinations of 2 categorical variables), lets call the groups A+B-, A+B+, ...
0
votes
0answers
1 view

Comparing means in a small panel before and after an intervention

I have 24 retirement communities and I know the healthcare costs for them in years 1 through 4. In year 4, there was an intervention where people identified as high risk benefited from a program ...
0
votes
1answer
51 views

How we can compare two coefficients of one linear regression?

I have this regression model, $$\hat{Y}=\hat{a}X_1+\hat{b}X_2+\hat{c}$$ Both $X_1$ and $X_2$ are significant at 0.01 level. $X_1$ and $X_2$ have a same unit. Now I want to find a test that tells me ...
0
votes
1answer
32 views

T-test for Bernoulli Distribution- Sample or Population data for SE calculation?

Am struggling to understand part of the answer to a question have done- Qu- In a given population, 11% of the likely voters are African American. A survey using a simple random sample of 600 landline ...
0
votes
0answers
42 views

Finding a mean value so that the t-test results in a p-value < 0.05

Basically, given mean 1, I need to find the maximum value of mean 2 below mean 1 so that the t-test results in a p-value < 0.05. What could be the "best approach" for doing such "reverse t-test"?
2
votes
1answer
43 views

Regression coefficients tests before or after model selection

I have a set of data containing 4 predictors (environmental conditions and animal size) and one predicted variable (animal growth rate). I want to fit a regression model to this data. I have two ...
0
votes
1answer
12 views

How to analyse extremely low sample pre/post test data?

So the study involves assessments, then an intervention, and then the same assessments. There are two groups, 2 in one group, 1 in the other. Data is not binary but consists of scores on the ...
1
vote
0answers
26 views

Frequentist statistics

Frequentist inference is the only form of statistics taught in my department, and I feel like it has a strong hold over many students here. But when I read data science blogs, I get the feeling that ...
0
votes
1answer
20 views

Can we do a T-Test when we have two columns of average data?

I have a data set assume as shown below: I wanted to know that can I use a paired T-Test to test if the average time spent is different Pre and Post change? (I am a little unsure because the each ...
0
votes
0answers
18 views

Asking input for this test scenario (Welch ANOVA instead of t-Test for two sample data)

I am asking for suggestions and comments on this test setup as I have not run tests with this type of data before. I am seeking to verify a (fishy) theory according to which economic downturns in the ...
0
votes
1answer
18 views

Two sample t-test with equal variance - two equations

The equation for this test is the following (that's how it is stated in most texts). I got a proof that it indeed has a t-distribution: ...
1
vote
1answer
25 views

How t multiplier is calculated from df and 95% confidence interval?

The appropriate t-multiplier for a 95% confidence interval for the mean $\mu$ is t(0.025,14) = 2.15. How to get this value 2.15? Is there any formula ?
1
vote
1answer
21 views

Unequal sample sizes in t test with homogeneity of variance

I have looked at the other similar questions on here, but I can't seem to understand whether power is still an issue for unequal sample sizes with the homogeneity of variance being met. Yuen (1974) ...
0
votes
1answer
22 views

T-test: is the difference of the means in my sample's two subgroups equal to a given difference of means?(SPSS)

I've recently reread the section about t-test, comparing means in two independent subgroups and know the formula, how to compute the t-coefficient. Now I'm facing the question, whether the difference ...
2
votes
0answers
23 views

Comparing means of two samples, one with 2million+ samples, other with only 200

I have two sets of data and a metric associated with each of them, I want to see if one category of data (e.g. males) have a tendency to have ahigher metric associated with it than the other category ...
0
votes
0answers
5 views

Comparing a sample's mean to the population's mean from which it was taken

Let's say I had Population A (N=1200). Population A is composed of 1200 Sample areas each with their own mean/SD, etc. Let's us assume that taking all of these Samples together is the entire ...
1
vote
1answer
32 views

Can I do a Binomial test on more than one individual/group? Can a repeated t test have different sample sizes?

I've conducted an experiment on chickens, training them to associate either blue or yellow with a 30 or 1 second wait before a food reward and then giving them a preference test, 15 times in total and ...
0
votes
0answers
13 views

Canceling a confound with linear regression?

I would like to compare variables $X$ and $Y$. However, I notice that both are effected by some confounding variable $Z$. I do linear regression on $X$ and $Y$ with $Z$ and find that ...
0
votes
0answers
17 views

How can I test which timepoints are different between treated groups and control group?

Which test should I use to find out which tested days are sigificantly different between treated (red and blue) and control group (dashed) ? I don't want full cross-testing between all categories, ...
1
vote
1answer
23 views

Computing required sample size for paired t-test

I have some paired t-test data (40 pairs) and I would like to use these data to estimate the sample size required if I were to conduct the study again with a new set of requirements. I'm using ...
1
vote
1answer
37 views

Overlapping standard errors and statistical significance

I have a paired data set which I have placed into $x$ and $y$ columns where $x$ are the control values and $y$ are the values following drug treatment. $N=10$ for both $x$ and $y$ columns as they are ...
0
votes
1answer
27 views

Statistics test to compare counts

I have two processes that produce the same type of event. For example, after 48 hours I may have 10,321 events from one process and 11,548 events from the other. What statistical test do I use to ...
2
votes
1answer
45 views

What happens when there's a one-tailed hypothesis test and the results are in the other tail?

For example, let's say I'm using a one-tailed t-test to see if a box of Lucky Charms cereal has more than 100 marshmallows. I know the consequences of using a one-tailed t-test and how it wouldn't be ...
0
votes
0answers
23 views

Comparing means of different training programs in R

I have a data set with performance and training data that looks something like (this is not the exact data, but gives a general idea): ...
2
votes
0answers
43 views

How do I use weight vector of SVM and logistic regression for feature importance?

I have trained a SVM and logistic regression classifier on my dataset for binary classification. Both classifier provide a weight vector which is of the size of the number of features. I can use this ...
2
votes
1answer
36 views

When to apply FDR procedure when doing many t-tests for many dependent variables?

I'm looking to run a bunch of t-tests, and I'm trying to figure out the appropriate time to apply an FDR correction. I have four conditions and am doing pairwise comparisons amongst these conditions, ...
4
votes
3answers
133 views

What follows if we fail to reject the null hypothesis?

What conclusions can we draw if $p>\alpha$? Does not rejecting the $H_0$ mean anything?
0
votes
0answers
23 views

Statistical test with unequal sample sizes

If I have two samples with vastly different sample sizes (say n1 = 800 and n2 = 21,000) what statistical test would give me the most reliable results? I've been using the Mann Witney U test. Is the ...
1
vote
2answers
40 views

T-test with only certain values that form the mean and standard deviation

If I'm running a simple 1-sample t-test, and I have x-bar, s, n, and mu, where p-hat and s come from the following type of numbers: ...
1
vote
1answer
34 views

Am I causing statistical violations? [closed]

I am trying to analyze where the significant differences are between 2 sets of time series. Group 1 (Expert) has 29 trials normalised to 256 points whereas Group 2 (Novice) has 19 trials (see attached ...
1
vote
1answer
70 views

Interpreting test results on log-transformed data

I have data that is not normally distributed. I can log-transform it to be normally distributed, and then perform, for example, a t-test. But how do I interpret the results of the t-test? Do I have ...
1
vote
1answer
31 views

Using a t-test for paired proportions

This is something that I'm having trouble verifying on Google, so I'm asking here as a sanity check. I have data collected randomly (not equally) over time for different users. To determine if some ...
1
vote
1answer
40 views

t-test in large, unequal sample size + additional info such as effect size

I have 2 samples, named "1" and "3": (1) n = 1282, mean = 14.77, sd = 8.27 (3) n = 5360, mean = 15.88, sd = 8.55 Their distribution look: ...
1
vote
1answer
31 views

Equivalence of the dt and pt function in R

in my own curiosity I decided to question the equivalence of dt and pt in R. pt denotes the cumulative density function of the t-distribution. So this gives us $P(X \le x)$. So if I want to find the ...
1
vote
1answer
25 views

How to combine 2 unpaired t tests that test the same effect

I have am studying an effect that degrades device quality and performed an independent sample test on two batches that had different initial quality. I would like to make the strongest statement ...
0
votes
0answers
12 views

Calculate Sample Size for a Price Change for Specific Group

Say I operate a tour bus. For every tour I run, I offer guests the option to buy a camera. The camera currently costs 5. I know average purchase rate is 40 percent and the standard deviation per ...
0
votes
0answers
14 views

Comparing multiple effects of treatment

I am measuring gait in PD patients undergoing surgery. I measure them pre-operation and then at 6 months post-operation. I want to answer the question how does their gait improve. I am reporting 13 ...
0
votes
0answers
11 views

Interpreting Tukey test for significant differences

Hi I have 38 categories and I have their means. I want to see if the differences in means are significantly different. I ran an anova and the p-value is <2e-16. Then I wanted to investigate ...
0
votes
0answers
5 views

Spearman correlation and ranksum test for 2-class problems

While Pearson correlation and 2-sample T test give the same p value and the correlation coefficient can be easily converted into t-value in 2-class problems, Spearman correlation and Wilcoxon ranksum ...
1
vote
1answer
31 views

Testing the difference between two samples with very different sizes using an un-paired t-test

I want to test wether population A is significantly different from population B (at 5% confidence interval). I need to do it for each variable using an un-paired t-test, since my data are normally ...
0
votes
1answer
36 views

Why is the degree of freedom in t.test dependent on setting of digits?

This seems to be a very basic problem but I just can't seem to figure out why it happens. Why is the degree of freedom in t.test in ...
0
votes
0answers
11 views

Statistical significance in a small peer group

I am looking at the gross profit margins in a industry where there are 10 companies. The company I am interested in has a gross profit margin of 28% and the mean gross margin across all 10 companies ...
0
votes
0answers
11 views

Mean accuracy confidence intervals with “corrected resampled t-test statistic”

I'm interested in calculating the expected prediction accuracy of my machine learning algorithm. My datasets only contain a small number of sample, so to do this, I repeat k-fold cross validation ...